The long-term objective is to understand in detail the morphogenesis of a relatively simple animal virus, namely reovirus. More specifically we are studying the replicating and encapsidation of the 10 segments of reovirus genome RNA. In the past year we have shown that double-stranded reovirus genome RNA is synthesized within virion-like particles and that therefore 10 segments of single-stranded RNA are encapsidated and subsequently replicated. We will a) study the mechanism by which 10 segments of single- stranded RNA are encapsidated; b) determine the nature of several non- infectious subviral particles which we have isolated from infected cells and which contain double-stranded RNA and c) try to develop a cell-free system which will support steps in viral morphogenesis.